Calculation of depth and speed of objects with coded pulses based on speed changes of ultrasound/sound

ABSTRACT

During transmission, a speed of ultrasound pulses gradually reduces due to acoustic impedance. A length and a density and a sound speed of the ultrasound pulses decide their average speed in the transmitting medium, frequencies, sound intensity and detecting depth. Time of flight (TOF) and TOF shift can be used to calculate the depth and moving speed of detecting objects. Calculating a speed of moving objects by simultaneously detecting TOFs at one detecting site from two separated piezoelectric (PZT) elements improves the testing results with accuracy, simplification and reproducibility. Coding ultrasound pulses to obtained the TOF and the TOF shift can be used to simultaneously calculate the depth and the moving speed of the objects, which also avoids a problem of an aliasing for highly moving speed of the objects. Coding ultrasound pulses also improves the quality of the imaging.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority to U.S. patent application Ser. No.13/341,928 filed on Dec. 31, 2011, and U.S. patent application Ser. No.14/305,074 filed on Jun. 16, 2014, and U.S. patent application Ser. No.14/532,125 filed on Nov. 4, 2014, and U.S. patent application Ser. No.14/645,475 filed on Mar. 12, 2015, the entire contents of all of whichare incorporated herein by reference.

FIELD OF THE DISCLOSURE

The present disclosure generally relates to the field ofsound/ultrasound technology and, more particularly, relates to a methodfor calculation of detecting depth and speed of moving objects based onspeed changes of sound/ultrasound.

BACKGROUND

Transmission of ultrasound pulses is actually energy traveling ofacoustic pulses in transmitting medium. If there is acoustic impedanceduring the transmission of the ultrasound pulses, the acoustic impedancewill resist the movement of the ultrasound pulses. Currently, it issupposed that speed of the ultrasound pulses is identical in the samemedium during the transmission. But, in the invention, the speed of theultrasound pulses is considered as gradually reduced during thetransmission due to the acoustic impedance of the transmitting medium,which gradually depletes the energy of the ultrasound pulses. Accordingdirect relationship between the acoustic impedance and the speed of theultrasound pulses in the transmitting medium, higher speed of theultrasound pulses will meet higher acoustic impedance and consume moreits energy during the transmission. So, the question is if the speed ofthe ultrasound pulses can still keep the same as currently supposed whenits energy is gradually reduced until exhausted? If the speed of theultrasound pulses is gradually reduced during transmission, thedetecting depth may be wrong based on calculating the detecting depthwith fixed ultrasound speed for the ultrasound pulses with differentfrequencies.

Current ultrasound theory connects frequencies of the ultrasound pulseswith their detecting depth, with lower frequency of the ultrasoundpulses having deeper detecting depth. But, a thin piezoelectric (PZT)element can make the ultrasound pulses with a high frequency as well asa low frequency, which means the ultrasound pulses with both frequenciessending from the same PZT element have the same level of energy. So, thequestion is what are main factors that affect the detecting depth of theultrasound pulses?

Ultrasound pulses can be reflected by motionless or moving objects, andaccording Doppler theory, it is currently considered that forward movingobjects can compress the frequency of the ultrasound pulses andreversely moving objects decompress the frequency of the ultrasoundpulses. So, Doppler mechanism has been widely used to measure thevelocity of the moving objects based on frequency shift, such as medicalultrasound machine and Doppler radar. For the pulsed wave ultrasound,aliasing is explained with insufficient Doppler sampling rate of thefrequency domain analysis. But, the theory of the frequency domain cannot completely solve the aliasing problem of the pulsed wave ultrasoundand the color ultrasound.

Thus, there is a need to overcome above problems to provide methods formore accurately calculating the detecting depth of ultrasound pulses,increasing the detecting depth of high frequency ultrasound, correctlycalculating the speed of the moving objects and correcting the aliasingfor the pulsed wave and the color ultrasound.

BRIEF SUMMARY OF THE DISCLOSURE

One aspect of the invention, correcting the transmitting distance ofultrasound pulses can rectify the registration of the detecting depth,which improves the quality of ultrasound images. Currentsound/ultrasound theories and applications are based on the identicalaverage speed in the same transmitting medium with various frequenciesof the ultrasound pulses. But, the invention is based the speedreduction of sound/ultrasound during the transmission in the medium dueto the loss of their energy caused by acoustic impedance. Forultrasound, calculating of the detecting depth of ultrasound pulsesbased on the identical average speed of the ultrasound pulses will causemiscalculation of the detecting depth due to different average speedsfor the ultrasound pulses with different frequencies. Because a lengthand a density of the ultrasound pulses can affect the average speed ofthe ultrasound pulses, they can be used to calculate the ultrasoundspeed reducing coefficient and correct the registration of detectingdepth of ultrasound pulses, which improve the quality of images.

In another aspect of the invention, changing thickness and density ofpiezoelectric (PZT) elements and sound speed in the PZT elements canregulate intensity of the ultrasound pulses, which affect theirdetecting depth. The detecting depth of the ultrasound pulses is notdirectly related to their frequencies, but related to the intensity ofthe ultrasound pulses. The thickness and the density of PZT elementsdecide the length and density of the ultrasound pulses, and the soundspeed in the PZT elements decides the maximal speed of the ultrasoundpulses in the transmitting medium. So, selecting the PZT with greaterdensity and higher speed of ultrasound pulses in the PZT elements willincrease the detecting depth for high frequency ultrasound.

Another aspect of the invention is detecting the speed of moving objectsbased on time of flight (TOF) shift of time domain analysis for acontinuous wave, a pulsed wave and a color ultrasound. It is based onthe speed changes of reflected ultrasound pulses by the moving objects,which change the TOF and the TOF shift of the ultrasound pulses. Nomatter in the continuous wave or the pulsed wave or the colorultrasound, when checking the speed of blood flow, the ultrasound systemalways detects the reflected ultrasound pulses from certain locationswhere ultrasound beam cross with blood vessels to calculate the TOFshift. So, the speed of the moving objects can be calculated based onthe TOF shift. A angle between ultrasound beams and a direction ofmoving objects decides the value of the TOF shift. Calculating the speedof moving objects by simultaneously detecting TOF from two separated PZTelements from same gate avoids the effect of tortuous blood vessels andvariant performances of sonographers, which improves the testing resultswith accuracy, simplification and reproducibility.

In the invention, the theory of above TOF and TOF shift can be used tocompletely correct an aliasing for the pulsed wave and the colorultrasound no matter how fast the speed of the moving objects will be. Acalculated TOF is based on the average speed of ultrasound pulses in thetransmitting medium and distance between transducer and the gate. Adetected TOF is the time that the ultrasound system interprets fromemitted ultrasound pulses and reflected ultrasound pulses. An actualTOF, which is an actual traveling time of the ultrasound pulses betweentransducer and the detecting objects. If the speed of the moving objectsis too fast, which makes the actual TOF excesses its aliasing limit, theultrasound system will misinterpret the reflected ultrasound pulses andgenerate the aliasing TOF. For the forward moving objects, the aliasinglimit for the actual TOF is less than the value of half calculated TOF.If the actual TOF is smaller than the aliasing limit, the ultrasoundsystem will misinterpret the reflected ultrasound pulse and add a valueof calculated TOF into the actual TOF, which generates the aliasing TOF.Then the aliasing TOF is greater than the calculated TOF. So, thealiasing TOF shift is below the baseline, which represents the movingobjects toward opposite direction. For reversely moving objects, theirTOF aliasing limit is that the actual TOF is greater than the value ofone and half calculated TOF. If the actual TOF is greater than itsaliasing limit, the ultrasound system will misinterpret the detected TOFand subtract a value of calculated TOF from the actual TOF. Then thealiasing TOF is smaller than the calculated TOF. So, the aliasing TOFshift is above the baseline, which represents the moving objects asforward direction. So, in the invention, a computer program is designedto identify and correct the aliasing TOF shift no matter how fast thespeed of the moving objects will be. Identifying and correcting thealiasing TOF shift can also be used to differentiate the colors ofaliasing from the colors of the turbulent flow, which benefits clinicaljudgment and diagnosis.

The continuous ultrasound doesn't contain information of depth and thepulsed wave ultrasound may generate a problem of aliasing. In theinvention, a method of coding ultrasound pulses is used to takeadvantages of the continuous wave ultrasound and the pulsed waveultrasound, which can obtain information of depth and speed of thedetecting objects at the same time, and avoid the aliasing. Within eachpulse duration, different numbers of ultrasound pulses are sent, whichis assigned a pulse character. Coded pulse characters are emitted with asame rest period, which is between each pulse duration. Coding pulsecharacters endow each pulse character with information of a sendingtime. The TOF of the pulse characters can be obtained between the timeof sending the pulse characters and receiving the same pulse characters,and TOF shift can be obtained from the difference of sending rest periodand receiving period of the pulse characters. Therefore, the depth andthe speed of the detecting objects can be obtained from the TOF and theTOF shift.

Based on the speed reduction of the ultrasound/sound during thetransmission, the intensity of the ultrasound pulses, the TOF, and theTOF shift can more accurately present the relationship between theultrasound pulses with the depth and the speed of the detecting objectsthan the results from the identical ultrasound speed and the Dopplershift. Other aspects or embodiments of the present disclosure can beunderstood by those skilled in the art in light of the description, theclaims, and the drawings of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings are merely examples for illustrative purposesaccording to various disclosed embodiments and are not intended to limitthe scope of the present disclosure.

FIG. 1 is a schematic illustration of rebound force of forward flow toultrasound pulse;

FIG. 2 is a schematic illustration of rebound force of reversed flow toultrasound pulse;

FIG. 3 a is a schematic illustration of spectrum for TOF shift ofcontinuous wave ultrasound;

FIG. 3 b is a schematic illustration of TOF shift and the profile of TOFshift for forward moving objects of pulsed wave ultrasound;

FIG. 3 c is a schematic illustration of TOF shift and profile of TOFshift for reversely moving objects of pulsed wave ultrasound;

FIG. 4 is a schematic illustration of aliasing TOF and aliasing TOFshift

FIG. 5 a is a schematic illustration of profile of aliasing TOF shiftfor forward flow of pulsed wave ultrasound;

FIG. 5 b is a schematic illustration of profile of corrected TOF shiftfor forward flow of pulsed wave ultrasound;

FIG. 6 a is a schematic illustration of profile of aliasing TOF shiftfor reversed flow of pulsed wave ultrasound;

FIG. 6 b is a schematic illustration of profile of corrected TOF shiftfor reversed flow of pulsed wave ultrasound;

FIG. 7 is a schematic illustration of computer program to calculate TOFshift of continuous wave ultrasound;

FIG. 8 is a schematic illustration of computer program to identify andcorrect aliasing TOF shift, and calculate the speed of moving objectsfor pulsed wave and color ultrasound;

FIG. 9 is a schematic illustration of the color of aliasing in colorultrasound;

FIG. 10 is a schematic illustration of the colors of turbulent flow incolor ultrasound;

FIG. 11 is a schematic illustration of computer program to differentiatethe color of turbulent flow from the color of aliasing and correct colorof aliasing based on TOF shift; and

FIG. 12 is a schematic illustration of calculation of detecting depthand moving speed of objects with coded ultrasound pulses; and

FIG. 13 is a schematic illustration of calculation of speed of movingobjects with two separated PZT elements.

DETAILED DESCRIPTION

Reference will now be made in detail to exemplary embodiments of thedisclosure, which are illustrated in the accompanying drawings. Whereverpossible, the same reference numbers will be used throughout thedrawings to refer to the same or like parts.

Speed of Ultrasound Pulses Gradually Reduces During Transmission

Transmitting in a medium, a sound pulse contains its energy, whichdecides its sound intensity. A pulse of the sound intensity includes itslength, density and speed. The length and density of the sound pulse isrelated to thickness and density of materials that create the sound. Thethicker material gives a longer sound pulse, which is like differentsounds from different chords of a violin or a piano. The density of thesound is related to density of materials that create the sound. Thehigher density of the materials is, the greater density of the soundwill be, such as the sound difference launched from wood or metal. Thesound speed is also related to the speed sent from the material, such asdifferent sound strength when hitting a key of a piano with differentforces. Hitting the key more strongly will bring louder sound, which isrelated to faster sound speed. So, the intensity of the sound pulse isthe multiplication value of its length, density and speed. A sound pulsewith greater intensity will travel further, and the speed of the soundpulse will gradually reduce due to the acoustic impedance oftransmitting medium, which gradually depletes the energy of the sound.

Sound intensity(kg/MS)=sound length(M)×sound density(Kg/M³)×soundspeed(M/S)

M=meter; Kg=kilogram; S=second

Piezoelectric elements (PZT) in a transducer of ultrasound machine emitultrasound pulses with their intensity, which is related to the length,density, and speed of the ultrasound pulses. Nowadays, the speed of theultrasound pulses with different frequencies is considered as identicalin the same medium. But, actually the speed of the ultrasound pulses isnot fixed at the same speed as supposed during the transmission, and itwill gradually reduce due to an acoustic impedance of the transmittingmedium. As bullets shooting from a machine gun, their speed is graduallyreduced due to loss of their energy caused by resistance of air. But,frequency of the bullets at any sites of trajectory may be kept thesame. The transmission of the ultrasound pulses has the similarmechanism. The acoustic impedance is decided by density of thetransmitting medium and the average speed of the ultrasound pulses inthe transmitting medium. During the transmission, the speed of theultrasound pulses gradually reduces due to the loss of their energycaused by the acoustic impedance, which will finally exhausts the energyof the ultrasound pulses. But, Ultrasound pulses keep the same frequencyduring the transmission, including their reflected frequency. A rate ofthe speed change of the ultrasound pulses is related to the density ofthe transmitting medium, sound speed in the transmitting medium, and thelength and density of the ultrasound pulses. So, a speed reducingcoefficient can be used to express their relationship with the speedchanges.

Calculation of Detecting Depth of Ultrasound Pulses Based on SpeedChange of the Ultrasound Pulses

One aspect of the invention is calculation of detecting depth of theultrasound pulses based on the speed reduction of the ultrasound pulsesduring the transmission. Nowadays, calculating the detecting depth isbased on an average speed of the ultrasound pulses in the transmittingmedium, and the average speed of the ultrasound pulses is considered asidentical for the ultrasound pulses with different frequencies in atransmitting medium, which may miscalculate the detecting depth due to avariation of the average speed of the ultrasound pulses with thedifferent frequencies. As the ultrasound pulses leave the PZT elementsand enter the transmitting medium, the speed of the ultrasound pulses isat their maximal speed. Then, under effect of the acoustic impedance,the speed of the ultrasound pulses will gradually reduce during thetransmitting process. The longer the ultrasound pulses travel, theslower the speed of the ultrasound pulses will be. So, the speedreducing coefficient of the ultrasound pulses can be used to calculate adistance shift. The speed reducing coefficient is directly proportionalto the density of the transmitting medium and the sound speed in the PZTelements, and inversely proportional to the length and density of theultrasound pulses. The sound speed in the PZT elements is directlycorrelated to the maximal speed of the ultrasound pulses in thetransmitting medium as they enter the transmitting medium. The depthshift is caused by speed reduction of the ultrasound pulses during thetransmission. The depth shift of the ultrasound pulses is a half valueof multiplication result of the speed reducing coefficient and maximalspeed in the transmitting medium and traveling time of the ultrasoundpulses. V_(m) is a maximal speed of the ultrasound pulses as they justenter a transmitting medium. t is the traveling time from emitting toreceiving the ultrasound pulses. V_(avg) is a average speed of theultrasound pulses in the transmitting medium. The detecting depth is ahalf value of multiplication result of the average speed and thetraveling time.

${{Speed}\mspace{14mu} {reducing}\mspace{14mu} {coefficient}} = \frac{{medium}\mspace{14mu} {density} \times {sound}\mspace{14mu} {speed}\mspace{14mu} {in}\mspace{14mu} {PZT}}{{PZT}\mspace{14mu} {density} \times {PZT}\mspace{14mu} {thickness}}$Depth shift=speed reducing coefficient×V _(m) ×t/2

$\begin{matrix}{{{Detecting}\mspace{14mu} {depth}} = {{V_{m} \times {t/2}} - {{Depth}\mspace{14mu} {shift}}}} \\{= {V_{m} \times \left( {1 - {{speed}\mspace{14mu} {reducing}\mspace{14mu} {coefficient}}} \right) \times {t/2}}}\end{matrix}$V _(avg) =V _(m)×(1−speed reducing coefficient)

Detecting depth=V _(avg) ×t/2

Currently there is just one average speed of the ultrasound pulses ineach transmitting medium. For instance, the speed of the ultrasoundpulses in the soft tissue is about 1540 meter/second. But a change ofthe length or density of the ultrasound pulses affects their averagespeed in the transmitting medium. Such as there may be a difference ofthe speed reducing coefficient between the ultrasound pulses with 4 MHzand the ultrasound pulses with 8 MHz because of the difference of thelength of the ultrasound pulses. So, their average speed in the softtissue may be different, and their detecting depth may be also differentat the same traveling time. Calculating the detecting depth with a fixedaverage speed may cause an error in their actual traveling depth.Because multiple factors affect the energy and the speed of theultrasound pulses, such as reflection, absorption and scattering, themathematic equation of the average speed of the ultrasound pulses justmainly reflects a relationship of the average speed with the length ofthe ultrasound pulses, which represents different length of theultrasound pulses with different average speed. Therefore, it isnecessary to more accurately calculate the detecting depth based on thedifferent average speed of the ultrasound pulses in the transmittingmedium according to the change of the length of the ultrasound pulses.

The Intensity of the Ultrasound Pulses Affect Their Detecting Depth

In another aspect of the invention, increasing the intensity of theultrasound pulses increases their detecting depth. As the powertransferred per unit area, the intensity of the ultrasound pulses equalsthe multiplication value of the length, density and speed of theultrasound pulses. Increasing one or more of the thickness and thedensity of PZT elements and sound speed in the PZT elements increasesthe intensity of the ultrasound pulses, which increase their detectingdepth.

In current ultrasound theory, the attenuation coefficient is directlyproportional to the frequency of the ultrasound pulses. The lower thefrequency of the ultrasound pulses is, the smaller the attenuationcoefficient will be. As the frequency of the ultrasound pulses isinversely proportional to the thickness of the PZT elements, the morethickness of PZT has lower frequency of the ultrasound pulses.

Frequency=sound speed in PZT/2×PZT thickness

attenuation coefficient(dB/cm)=frequency (MHz)/2

Actually, the thickness and the density of the PZT elements are directlyrelated to the length and density of the ultrasound pulses, which affectthe intensity of the ultrasound pulses. The more thickness and thedensity of the PZT elements are, the greater length and density of theultrasound pulses will be, which increase the intensity of theultrasound pulses. As a heavier ball has ability of further travelingdistance, the ultrasound pulses with greater intensity will have greaterpenetrating depth. The speed of the ultrasound pulses in the PZTelements is directly correlated to a characteristics of the PZT elementsand a of electric output on the PZT element. So, changing the thicknessand the density of the PZT elements and the sound speed in the PZTelements can regulate the intensity of the ultrasound pulses and theirdetecting depth.

Sound intensity=sound length×sound density×sound speed

Sound intensity=acoustic impedance×traveling distance of ultrasoundpulses

Increasing Detecting Depth for High Frequency Ultrasound by Increasingthe Density of PZT Elements and Sound Speed in the PZT Elements

Currently, in order to increase the frequency of the ultrasound pulses,the thickness of the PZT elements is reduced, which decreases the lengthof the ultrasound pulses and their detecting depth. But, in theinvention, selecting the PZT materials with higher sound transmittingspeed and increasing electric output on the PZT elements will increase afrequency of the ultrasound pulses. At the same time, increasing thedensity of the PZT elements increases the density of the ultrasoundpulses, but not just decreasing the thickness of the PZT elements, itwill increase the frequency as well as the intensity of the ultrasoundpulses. As the result, it increases the detecting depth for highfrequency ultrasound.

Frequency=sound speed in PZT/2×PZT thickness

Improving Axial Resoultion of the Ultrasound Pulses by DecreasingThickness of the PZT Elements

Currently increasing frequency of the ultrasound pulses is used toincrease axial resolution. Actually, the axial resolution is decided bylength of the ultrasound pulses, which is related to the thickness ofthe PZT elements. But, the frequency of the ultrasound pulses is notdirectly related to the axial resolution of the ultrasound pulses,because thin PZT elements can generate high frequency as well as lowfrequency of the ultrasound pulses. Less thickness of the PZT elementsgenerates shorter ultrasound pulses and smaller numerical values ofspatial pulse length, which improve the axial resolution.

At the same time, the thickness of the PZT elements also limits thehighest frequency a ultrasound system can reach, which is less than avalue of sound speed in PZT elements divided by a length of theultrasound pulses.

Highest frequency<sound speed in PZT/PZT thickness

Moving Objects Change TOF and TOF ShiftIof the Ultrasound Pulses

Nowadays, Doppler mechanism is widely used to detect the speed of movingobjects. According Doppler mechanism, a distance of sound resources,such as a coming or leaving motorcycle, is changing. Therefore, afrequency of sound pulses emitted from an engine of the motorcycle isrelatively compress or decompressed due to the movement, which can beused to calculate to its speed.

As containing the energy, the ultrasound pulses can be reflected bymotionless or moving objects. No matter in the continuous wave or thepulsed wave or the color ultrasound, when checking speed of blood flow,the ultrasound system always detects the reflected ultrasound pulsesfrom fixed locations where the ultrasound beam cross with blood vesselsto calculate TOF shift of the reflected ultrasound pulses. So, distancesfrom the reflecting sites are fixed. It is more like playing tabletennis, a racket hits a ball at a fixed location and changes a speed ofthe reflected ball, which changes its TOF. Comparing to motionlessobjects, moving objects will change the rebounding force to theultrasound pulses. As in the FIG. 1, forward moving objects willgenerate the forward rebound force shift against the ultrasound pulses.The forward rebounding force shift is decided by a speed and an angle θof the moving objects with the ultrasound beam. The faster speed of themoving objects and smaller angle θ will generate greater forwardrebounding force shift, which increases the speed of the reflectedultrasound pulses. The smallest angle θ is zero. So, its TOF isdecreased and smaller than the TOF from motionless objects (baseline).As the result, the TOF shift is increased and above the baseline. On thecontrary, as in the FIG. 2, reversely moving objects will generatereversed rebounding force shift with the same direction of emittedultrasound pulses, which reduces the rebounding force. The faster speedof the moving objects and greater angle θ will create greater reversedrebounding force shift, which decreases the reflected speed of theultrasound pulses. The greatest angle θ is 180 degree. So, its TOF isincreased and greater than the baseline. As the result, the TOF shift isbelow baseline.

As the length and density of the ultrasound pulses is directlycorrelated to the thickness and density of the PZT elements, changingthe length and density of the ultrasound pulses also affects their TOFand TOF shift. For the forward moving objects, increasing the length anddensity of the ultrasound pulses will have smaller rate of increasedspeed of the reflected pulses. It elongates their TOF and reduces theirTOF shift. Decreasing the length and density of the ultrasound pulseshave greater rate of increased speed of the reflected ultrasound pulses,which will shorten their TOF and increase their TOF shift. For reverselymoving objects, increasing the length and density of the ultrasoundpulses will have smaller rate of decreased speed of the reflectedultrasound pulses. It shortens its TOF and decreases their TOF shift.Decreasing the length and density of the ultrasound pulses have greaterrate of decreased speed of the reflected ultrasound pulses, whichelongates their TOF and increase their TOF shift.

So, one aspect of the invention is calculating the speed of the movingobjects based on the TOF shift for the continuous wave or the pulsedwave or the color ultrasound. As mentioned above, the speed of theultrasound pulses will gradually reduce, and the moving objects willgenerate the rebounding force shift, which changes the speed of thereflected ultrasound pulses, their TOF and TOF shift. Therefore, the TOFshift can more accurately present relationship between the speed of themoving objects and characters of the ultrasound pulses.

Caluclating Speed of Moving Objects Based on TOF Shift for ContinuousWave Ultrasound

Currently, it is considered that speed of the ultrasound pulses is fixedin the same medium during the transmission. The moving objects willchange the frequency of the reflected ultrasound pulses. The forwardmoving objects will compress the reflected frequency, which is higherthan the emitted frequency. Its Doppler shift is above the baseline. Thereversely moving objects will decompress the reflected frequency, whichis lower than the emitted frequency. Its Doppler shift is below thebaseline. So, calculating Doppler shift of the continuous wave (CW)ultrasound is based on difference between the reflected frequency andthe emitted frequency. V_(objects) is a speed of the moving objects, fis a frequency of a transducer, and V is a speed of the ultrasoundpulses in a transmitting medium.

Doppler shift=reflected frequency−emitted frequency

${{Doppler}\mspace{14mu} {shift}} = \frac{2 \times V_{objects} \times f \times {\cos (\theta)}}{V}$

The invention discloses that a TOF shift of the CW ultrasound is used tocalculate the speed of the moving objects. The TOF shift of the CWultrasound is difference between a time of emitting period and a time ofreflected period. There are two PZT parts in CW ultrasound transducer.As in the FIG. 7, the emitting PZT part emits the continuous ultrasoundpulses with identical emitted period between previous and followingemitted ultrasound pulses (105), which is decided by the ultrasoundsystem. The receiving PZT part receives the reflected ultrasound pulsesand detects the reflected period between previously and followingreflected ultrasound pulses (106). The reflected period is decided bythe speed of the moving objects and the angle of the moving objects witha beam of the ultrasound pulses. If the ultrasound pulses are reflectedfrom motionless objects, the reflected period equals to the emittedperiod and their TOF shift is zero. So, the emitted period is set as abaseline, and the TOF shift equals zero at the baseline. Then, theultrasound system obtains the TOF shift from difference between theemitted period and the reflected period, and calculates speed of themoving objects according to the equation of the TOF shift (108).

emitted period=the time between previous and following emitted pulses

reflected period=the time between previously and following reflectedpulses

TOF shift=emitted period−reflected period

${{TOF}\mspace{14mu} {shift}} = \frac{2 \times V_{objects} \times f \times {\cos (\theta)}}{V_{avg}}$

As 101 in FIG. 3, the emitted period is the time between the previouslyand following emitted pulses, which forms the baseline. The reflectedperiod is the time between previously and following reflected ultrasoundpulses. If the ultrasound pulses are reflected from the moving objectsthat are vertical to the ultrasound beam (flow N), the emitted periodequals to its reflected period, and the TOF shift is zero. But, if theultrasound pulses are reflected from the forward moving objects (flowM), the speed of the reflected ultrasound pulses will be accelerated dueto the increasing rebounding force, which shorten the TOF M′. So, thereflected period will be less than the time of the emitted period, whichgenerates TOF shift M′ and is above the baseline. On the contrary, forthe reversely moving object (flow O), the TOF O′ will be elongated dueto the reduced rebounding force and the speed of the reflectedultrasound pulses. So, the reflected period will be greater than thetime of the emitted period, which generates the TOF shift O′ and isbelow the baseline.

As 100 in FIG. 3, for the CW ultrasound, a transducer receives all ofthe reflected ultrasound pulses from an area under the transducer. Ifthere are several moving objects with different velocities toward thetransducer, they will rebound the ultrasound pulses with differentreflected speeds and TOFs, which generate different TOF shifts relatedto these moving objects. Then the ultrasound system will trace andcompare a list of these reflected pulses and respectively present theirTOF shifts on TOF shift spectrum. For CW ultrasound, because there areusually multiple moving objects under the transducer with differentvelocities, such as multiple blood vessels, its TOF shift spectrum oftenpresents as spectral broadening as 102 in FIG. 3 a. So, a computerprogram can be used to calculate the speed of the moving objects basedon the values of the TOF shift as in FIG. 7.

Calculationg Speed of Moving Objects by TOF Shift for Pulsed Wave andColor Ultrasound

There is only one part of PZT elements in a transducer of the pulsedwave ultrasound, which sends and receives ultrasound pulses. So, thetransducer has to receive previously reflected pulses before sendingnext emitted pulses. In order to detect speed of the moving objects, agate is set with a certain distance. So, based on the average speed ofthe ultrasound pulses and the distance between the transducer and thegate, a calculated TOF can be obtained as A in FIG. 3 b, which is set asthe baseline, and the TOF shift at the baseline equals to zero. Thedetected TOF is that the ultrasound system interprets TOF from theemitted and reflected ultrasound pulses, which can be affected by themoving objects. The actual TOF is the time the ultrasound pulsesactually travel between the transducer and the gate. As the ultrasoundpulses leave a transducer and enter the transmitting medium, their speedis at maximal and will gradually reduce during the transmitting process.The moving objects will rebound the ultrasound pulses and change thedetected TOF, which generates the TOF shift between the calculated TOFand detected TOF. The calculated TOF is based on the average speed ofultrasound pulses in the transmitting medium. So, when the actual TOFexcesses its aliasing limit and the value of TOF shift is smaller thanthe value of a half calculated TOF, ultrasound system will misinterpretthe detected TOF, which generates the aliasing. Before the aliasing, thedetected TOF is the actual TOF, and after the aliasing, the detected TOFis the aliasing TOF. The TOF shift is difference between the calculatedTOF and the detected TOF. For a forward moving object, it acceleratesthe speed of the reflected pulses, which shorten its actual TOF as B inFIG. 3 b. So, the actual TOF is smaller than the calculated TOF, and theTOF shift is above the baseline. As increasing the speed of the movingobjects, the value of the detected TOF decreases and the value of theTOF shift increases, tip of the profile of the TOF shift is away fromthe baseline (80 in FIG. 3 b). On the contrary, reversely moving objectselongate their actual TOF, which is greater than the baseline, and theTOF shift is below the baseline. As the speed of the moving objectsincreases, the value of the detected TOF and the value of the TOF shiftboth increase, and the tip of the profile of the TOF shift is away fromthe baseline (82 in FIG. 3 c). Then the speed of the moving objects canbe calculated according the value of the TOF shift.

TOF shift=calculated TOF−detected TOF

${{TOF}\mspace{14mu} {shift}} = \frac{2 \times V_{objects} \times f \times {\cos (\theta)}}{V_{avg}}$

Identifying and Correcting Aliasing for Pulsed Wave Ultrasound

For the pulsed wave ultrasound, there is the aliasing, which is causedby the ultrasound system misinterpreting the detected TOF from thereflected ultrasound pulses. If the speed of the moving objects is toofast, and makes the actual TOF excesses its aliasing limit, theultrasound system will misinterpret it and the detected TOF becomes analiasing TOF. Then the aliasing TOF shift is located on opposite side ofthe baseline, which presents the moving objects as toward oppositedirection. The aliasing TOF shift also disrupts continuation of theprofile of the TOF shift.

For forward moving objects, the aliasing limit of the actual TOF is lessthan the value of half calculated TOF. if the actual TOF is smaller thanits aliasing limit, the ultrasound system will misinterpret thereflected pulses, and the aliasing TOF is a value of a actual TOF addinga calculated TOF, which is larger than the calculated TOF (104 in FIG.4). So, the aliasing TOF shift becomes below baseline, whichmisrepresents the moving objects moving toward opposite direction. Asthe result, before the actual TOF excesses its aliasing limit, the valueof the TOF shift is above the baseline(from E to F in FIG. 5). But,after the actual TOF excesses its aliasing limit, the value of thealiasing TOF shift is below the baseline(G and H in FIG. 5 a); As thespeed of the moving objects increases, both the value of the aliasingTOF and the value of the aliasing TOF shift decrease; and the tip of theprofile of the aliasing TOF shift is toward the baseline (81 in FIG. 5a), which discontinues the profile of the TOF shift.

Aliasing TOF=actual TOF+calculated TOF

Aliasing TOF shift=calculated TOF−aliasing TOF

Aliasing TOF shift=−actual TOF

So, in the invention, a computer program is designed to identify andcorrect the aliasing TOF shift. For the forward moving objects, theactual TOF is smaller than calculated TOF, and its TOF shift is abovethe baseline. As the speed of moving objects is increased, its actualTOF keeps decrease and smaller than the calculated TOF, and the TOFshift keeps increase and above baseline. But, after the actual TOFexcesses its aliasing limit, the aliasing TOF becomes greater than thecalculated TOF, and the aliasing TOF shift becomes below the baseline.The computer program will trace and compare the value of the followingTOF and TOF shift with the value of the previous TOF and TOF shift. Ifthe value of the TOF and the TOF shift approaches the value of halfcalculated TOF, and the value of following TOF shift is below thebaseline, which discontinues the profile of the TOF shift. It is thealiasing TOF shift. After identifying the aliasing TOF shift, theultrasound system will register the corrected TOF shift by subtractingthe value of the aliasing TOF shift from one calculated TOF (116 in FIG.8).

TOF shift=calculated TOF−actual TOF

Aliasing TOF shift=−actual TOF

corrected TOF shift=calculated TOF−|aliasing TOF shift|

After rectifying the registering errors of TOF shift, the value of thecorrected TOF shift will keep increase as increase of the speed of themoving objects, and the tip of the profile of the TOF shift is away fromthe baseline (84 in FIG. 5 b), which reestablish the continuation of theprofile of the TOF shift (FIG. 5 b), and the value of the correct TOFshift can be used to calculated the speed of the moving objects.

For the reversely moving objects, the rebounding force is reduced, whichdecreases the reflected speed of the ultrasound pulses and increasestheir TOF, which is greater than the value of the calculated TOF. So,the value of the TOF shift is below the baseline. For the reverselymoving objects, the aliasing limit of the actual TOF is larger than thevalue of one and half calculated TOF. If the value of the actual TOFexcesses its aliasing limit, the ultrasound system will misinterpret thereflected ultrasound pulses and the aliasing TOF is the value of theactual TOF subtracting a calculated TOF, which is smaller than thecalculated TOF. So, the aliasing TOF shift will be above the baseline;as the speed of the reversely moving objects keeps increase, thealiasing TOF is increased but the aliasing TOF shift is decreased, whichmake the tip of the profile of TOF shift is toward baseline (83 in FIG.6 a). As a result, the continuity of the profile of TOF shift isdisrupted (FIG. 6 a). In the invention, the computer program is used toidentify the aliasing. As the value of actual TOF is close to the valueof one and half calculated TOF and TOF shift approaches the value ofhalf calculated TOF, if following TOF shift is above the baseline, thealiasing TOF shift is identified.

Aliasing TOF=actual TOF−calculated TOF

Aliasing TOF shift=calculated TOF−aliasing TOF

Aliasing TOF shift=2×calculated TOF−actual TOF

After identifying the aliasing TOF shift, the computer program willrectify the aliasing TOF shift by subtract the value of a calculated TOFfrom the value of the aliasing TOF shift, which is based on followingequations:

TOF shift=calculated TOF−actual TOF

aliasing TOF shift=2×calculated TOF−actual TOF

correct TOF shift=aliasing TOF shift−calculated TOF

After correcting the aliasing TOF shift, the corrected TOF shift willincrease as the speed of the moving objects keeps increase, which makesthe tip of the profile of the corrected TOF shift away from thebaseline. The corrected TOF shift will reestablish the continuation ofthe profile of the TOF shift (FIG. 6 b), and it can be used to calculatethe speed of the moving objects.

Another method of avoiding the happening of aliasing is modifying thecomputer program in the ultrasound system to prevent adding orsubtracting the value of a calculated TOF into the detected TOF afterthe actual TOF excesses its aliasing limit.

Differentiating Color of Aliasing from Color of Turbulent Flows forColor Ultrasound

For the color ultrasound, ultrasound system automatically sets differentbaselines at regular distance along the ultrasound beam. The TOF fromreflected ultrasound pulses is compared with their respective baselineand get their TOF shift. Then colors are assigned according to a valueof the TOF shift to represent a velocity of the moving objects. But,there are similar color patterns between color of the aliasing and colorof turbulent flows. For the aliasing pattern, the color of the aliasingmistakenly presents as the moving objects toward opposite side after theactual TOF excesses its aliasing limit. For the turbulent flows, thecolor of the turbulent flows truly presents their moving direction. So,this will make the difficulties for clinical judgment and diagnosis forpathological situations. In the invention, differentiating the color ofthe aliasing from the color of the turbulent flows is based on thecharacters of the TOF shift of different colors.

For the color of the aliasing in FIG. 9, when a forward flow (S) passesa narrow part of vessel, the speed of a flow will be accelerated withinthe narrow part. If its actual TOF excesses its aliasing limit, thealiasing TOF shift marks the flow with a color of the aliasing (T) atthe narrow part, which represents the flow as toward opposite direction.Color of U represents the flow between the color of the no-aliasing Sand the color of the aliasing T, and the value of TOF shift for thecolor U is close to the value of half calculated TOF because the actualTOF for the color U is closing to its aliasing limit. From the color Tto the color U, or from the color S to the color U, their TOF shift isgradually increased until close to the value of half calculated TOF. Forthe color of the aliasing, the profile of the aliasing TOF shift will bemore close to the value of half calculated TOF with its tip of theprofile of the aliasing TOF shift toward baseline. But for the color ofthe no-aliasing (color S), the profile of the no-aliasing TOF shift willbe more close to the baseline with the tip of the profile of theno-aliasing TOF shift away from the baseline. Correcting the aliasingTOF shift is based on the direction of no-aliasing flow as forward orreversely moving direction. Then the color of the aliasing can becorrected based on the corrected TOF shift. The designed computerprogram in FIG. 11 will trace and identify the characters of the profileof the TOF shift for theses colors, and correct the color of thealiasing by rectifying their aliasing TOF shift.

But, for the color of the turbulent flows in FIG. 10, the color of Xrepresents a forward flow that enters in an enlarged part of a bloodvessel. The flow will become turbulent at the enlarged part of thevessel, and the color of Y represents a reversed blood flow. The colorof Z represents the edge between the flow X and the flow Y. The TOFshift for the color Z will be close to zero because its actual TOF isclose to its baseline. Because the speed of the flow is graduallydecreased to the edge Z, the TOF shift from one color to the edge ofanother color is gradually reduced until close to the zero. The tip ofthe profile of the TOF shift for both colors is away from the baselineand the profile of their TOF shift keeps its continuity. The colors offlows are assigned based on their TOF shift.

So, differentiating and correcting the aliasing TOF shift for the colorof aliasing from the TOF shift for the color of turbulent flows willbenefit the clinical judgment and diagnosis for truly pathologicalconditions.

Calculation of Speed of Moving Objects with Two Separated PZT ElementsWithout Need to Adjust the Angle of the Ultrasound Beam

The speed value of the moving objects is important in judging somepathological conditions, such as stenosis of blood vessels. The angle ofthe ultrasound beam with the direction of the moving objects decides thevalue of TOF shift, which affects the calculation of the speed of themoving objects. Currently in order to get accurate speed of the movingobjects, it is important to adjust the angle of the ultrasound beam withthe direction of the moving objects within 45 to 60 degree. But, thetortuous blood vessels and variant performances of sonographers oftenderive different speed values of the moving objects from a same testingsite, which increases the difficulties in the clinical diagnosis. In theinvention, by simultaneously checking the TOF shifts at one detectingsite from two separated PZT elements, the speed value of the movingobjects can be accurately calculated without the need to adjust theangle of the ultrasound beams with the direction of the moving objects,which simplifies the operating procedures and avoids the variation ofdetection.

As in the FIG. 13, after selecting a detecting site, two TOF shifts aresimultaneously detected from PZT A and PZT B, and an angle μ is betweentwo ultrasound beams from the PZT A and the PZT B, and an angle θ isbetween ultrasound beam from the ultrasound beam A with the direction ofthe moving objects. Therefore, their individual TOF shifts will beobtained, and the speed of the moving (V_(objects)) can be calculatedbased on the values of the TOF shifts, the transducer frequency (f), theangle μ and the average speed of the ultrasound pulses in thetransmitting medium (V_(avg)).

${{TOF}\mspace{14mu} {shift}\mspace{14mu} A} = \frac{2 \times V_{objects} \times f \times {\cos (\theta)}}{V_{avg}}$${{TOF}\mspace{14mu} {shift}\mspace{14mu} B} = \frac{2 \times V_{objects} \times f \times {\cos \left( {\theta + \mu} \right)}}{V_{avg}}$$V_{objects} = \frac{V_{avg} \times \sqrt{\begin{matrix}{\left( {{TOF}\mspace{14mu} {shiftA}} \right)^{2} - {2 \times {TOF}\mspace{14mu} {shiftA} \times}} \\{{{TOF}\mspace{14mu} {shiftB} \times {\cos (\mu)}} + \left( {{TOF}\mspace{14mu} {shiftB}} \right)^{2}}\end{matrix}}}{2 \times f \times {\sin (\mu)}}$

Calculation of Detecting Depth and Moving Speed of Objects with CodedUltrasound Pulses

Because the pulsed wave ultrasound causes the aliasing and thecontinuous wave ultrasound loses information of distance, a method ofcoding ultrasound pulses can combine advantages of the pulsed waveultrasound and the continuous wave ultrasound as well as avoid theirdisadvantages. This method is more like coding genomic sequence ofdeoxyribonucleic acid (DNA). A pulse duration is a time that ultrasoundpulses are sent. During each pulse duration, different numbers ofultrasound pulses are sent, which is assigned a pulse character. Forinstance, just one pulse within the pulse duration is assigned as apulse character A, two pulses as a pulse character C, three pulses as apulse character G, and four pulses as a pulse character T. A restingperiod is a time between each adjacent pulse duration, and the restingperiod for the emitted ultrasound pulses keeps identical. A transducerof the ultrasound system contains one pair or more of sending PZTelements and receiving PZT elements. The sending PZT elements sendultrasound pulses with specific coded pulse characters, such as ATC GCG. . . , which is like codes of a DNA sequence. By this way, it actuallyendows information of emitting time for each pulse character. Thereceiving PZT elements receive reflected ultrasound pulses, whichcontain the same codes of pulse characters, such as A′T′C′ G′C′G′ . . ., which contains information of receiving time for each pulse character.Therefore, TOF can be obtained from the time between the emitting timeand the receiving time of the related pulse characters. At the sametime, TOF shift can also obtained from the time difference of emittingresting time and receiving resting time of the related pulse characters.For instance, TOF of pulse character A can be obtained from a timebetween the emitted pulse character A and the reflected pulse characterA′, and TOF shift can be obtained from a time difference between theemitted resting period of the pulse character A and the receivingresting period of the pulse character A′. If reflections of theultrasound pulses from one point keep identical TOF and their TOF shiftis zero, it means the reflections coming from motionless objects. So,the TOF can be used to calculate the depth or distance of the motionlessobjects. If the TOF and the TOF shift keep variable, it means thereflections coming from moving objects. So, the TOF shift can be used tocalculate the speed of the moving object. Because the moving objectschange the TOF, which can not be used to calculate its actual location.By adding the TOF shift into the TOF, the TOF shift will compensate thechanged part of TOF. For the forward moving objects, the TOF shift ispositive, which will compensate shortened TOF. For the reversely movingobject, the TOF shift is negative, which will offset extended TOF. So, asum of the TOF shift with the TOF can be used to calculate the depth ordistance of the moving objects. The depth or distance of the movingobjects is a half multiplication value of the sum of TOF shift and TOFwith the average speed of ultrasound in the transmitting medium. Boththe speed and location of the moving objects can be used in imaging thecolor ultrasound. So, the method of the coded ultrasound pulses combinesthe advantages of the pulsed wave ultrasound and the continuous waveultrasound in the ultrasound system, which can obtain the information ofdistance and speed of the detecting objects at the same time (FIG. 12).It also avoids aliasing for detecting moving objects with high velocity.

Improving Imaging Quality with Coded Ultrasound Pulses

Because each PZT element may not only receive the reflected ultrasoundpulses emitted by itself but also receive the reflected ultrasoundpulses emitted from other PZT elements, which cause noise and artifacts,such as mirror image or refraction. The noise and artifacts will affectquality of ultrasound images. With each PZT element emits its specificcodes of the pulse characters, after receiving reflected ultrasoundpulses, the ultrasound system will compare the received codes of thepulse characters with the emitted ones, and register locations of thereflections that have the same received codes of the pulse characterswith the emitted codes of the pulse characters to an area belonging tothe PZT element that emits the codes of the pulse characters. By thisway, it may improve the noise and the artifacts.

Detecting Depth and Speed of Moving Objects in Other Applications ofSound

Ultrasound just occupies sound wave with frequencies of more than 20kilohertz. Actually sound pulses with any frequencies have the samemechanisms mentioned as above. So, the applications in detecting depthand calculating a speed of moving objects as mentioned above can be usedin the sound pulses with any other sound frequencies, such as radar andsonar.

Other applications, advantages, alternations, modifications, orequivalents to the disclosed embodiments are obvious to those skilled inthe art and are intended to be encompassed within the scope of thepresent disclosure.

What is claimed is:
 1. A method for calculating a detecting depth asspeed reduction of ultrasound pulses during a transmission, the methodcomprising: calculating a speed reducing coefficient of the ultrasoundpulses in a transmitting medium, wherein the speed reducing coefficientof the ultrasound pulses is directly proportional to the density of thetransmitting medium and the sound speed in the PZT elements, andinversely proportional to a density and a thickness of the PZT elements,which comprising:${{Speed}\mspace{14mu} {reducing}\mspace{14mu} {coefficient}} = \frac{{medium}\mspace{14mu} {density} \times {sound}\mspace{14mu} {speeding}\mspace{14mu} {in}\mspace{14mu} {PZT}}{{PZT}\mspace{14mu} {density} \times {PZT}\mspace{14mu} {thickness}}$obtaining an average speed (V_(avg)) of the ultrasound pulses in thetransmitting medium, wherein the average speed of the ultrasound pulsesis a difference between the maximal speed (V_(m)) of the ultrasoundpulses in the transmitting medium with a multiplication result of thespeed reducing coefficient and the maximal speed of the ultrasoundpulses in the transmitting medium, which comprising:V _(avg) =V _(m)×(1 −speed reducing coefficient); and determining adetecting depth, wherein the detecting depth is a half multiplicationvalue of the average speed and a traveling time of the ultrasound pulsesin the transmitting medium.
 2. A method of claim 1, further comprisingincreasing a intensity of the ultrasound pulses by increasing one ormore of a thickness of the PZT elements and a density of the PZTelements and a sound speed in the PZT elements, wherein the thickness ofthe PZT elements decides a length of the ultrasound pulses, and thedensity of the PZT elements decides a density of the ultrasound pulses,and the sound speed in the PZT elements decides the maximal speed of theultrasound pulses in the transmitting medium, a multiplication value ofthe length of the ultrasound pulses and the density of the ultrasoundpulses and the speed of the sound pulses decides the intensity of theultrasound pulses, which comprising:Sound intensity(kg/MS)=sound length(M)×sound density(Kg/M³)×soundspeed(M/S) M=meter; Kg=kilogram; S=second.
 3. The method of claim 2,further comprising increasing the intensity of the ultrasound pulses toincrease a detecting depth of the ultrasound pulses in the transmittingmedium.
 4. The method of claim 3, further comprising increasingdetecting depth for high frequency ultrasound by increasing the densityof the PZT elements and the sound speed in the PZT elements whereinincreasing the sound speed in the PZT elements and the density of thePZT increases the frequency of the ultrasound pulses as well as theirintensity.
 5. The method of claim 2, further comprising improving axialresolution by decreasing the length of the ultrasound pulses wherein thethickness of the PZT elements decides the length of the ultrasoundpulses as well as limits the highest frequency a ultrasound system canreach.
 6. A method of using time of flight (TOF) shift of the ultrasoundpulses to calculate a speed of moving objects in a continuous wave, apulsed wave and a color ultrasound, the method comprising: setting abaseline wherein the baseline is a span of traveling time of theultrasound pulses reflected from motionless objects at the same depth asfrom the moving objects, and a TOF shift equals to zero at the baseline;obtaining a detected TOF wherein the detected TOF is a traveling timethat a ultrasound system interprets from the reflected ultrasoundpulses, the detected TOF is related to the speed of the moving objectsand the angle of the moving objects with a ultrasound beam, and theintensity of the ultrasound pulses; calculating the TOF shift whereinthe TOF shift is a time difference between the baseline and the detectedTOF; and calculating the speed of the moving objects (V_(objects)) basedon an equation of TOF shift including the angle θ of the ultrasound beammade with the moving objects, an average speed (V_(avg)) of theultrasound pulses in the transmitting medium, the transducer frequency(f), wherein the TOF shift is the TOF shift for the continuous wave, thepulsed wave and the color ultrasound, the equation of the TOF shift is:${{TOF}\mspace{14mu} {shift}} = \frac{2 \times V_{objects} \times f \times {\cos (\theta)}}{V_{avg}}$7. The method of claim 6, further comprising calculating the speed ofthe moving objects by simultaneously detecting TOF shifts at one sitefrom two separated PZT elements, wherein the speed of the moving objectscan be calculated based on the values of the TOF shifts, the transducerfrequency, the angle μ between two ultrasound beams from the PZTelements and the average speed of the ultrasound pulses in thetransmitting medium as the following equation:$V_{objects} = \frac{V_{avg} \times \sqrt{\begin{matrix}{\left( {{TOF}\mspace{14mu} {shiftA}} \right)^{2} - {2 \times {TOF}\mspace{14mu} {shiftA} \times}} \\{{{TOF}\mspace{14mu} {shiftB} \times {\cos (\mu)}} + \left( {{TOF}\mspace{14mu} {shiftB}} \right)^{2}}\end{matrix}}}{2 \times f \times {\sin (\mu)}}$
 8. The method of claim6, further comprising changing the intensity and the angle of theultrasound pulses to regulate the speed of the reflected ultrasoundpulses wherein the changes of the speed of the reflected ultrasoundpulses alter the TOF and the TOF shift of the ultrasound pulses.
 9. Themethod of claim 6, further comprising a method of calculating the speedof the moving objects for the continuous wave ultrasound comprising:setting a time of a emitted period as the baseline wherein the time ofthe emitted period is the time between previously and following emittedpulses; obtaining a time of a reflected period as the detected TOFwherein the time of the reflected period is the time between previouslyand following reflected ultrasound pulses; calculating a TOF shiftwherein the TOF shift is a difference between the time of the emittedperiod and the time of the reflected period; and using the TOF shift tocalculate the speed of the moving objects based on the equation of TOFshift.
 10. The method of claim 6 further comprising a method ofcalculating the speed of the moving objects for the pulsed wave and thecolor ultrasound comprising: setting a time of a calculated TOF as thebaseline wherein the calculated TOF is the time that ultrasound systemcalculates according to a distance between a transducer and a gate andthe average speed of the ultrasound pulses in the transmitting medium;obtaining the detected TOF wherein the detected TOF is the time thatultrasound system interprets from ultrasound pulses traveling betweenthe transducer and the gate, before an aliasing the detected TOF is anactual TOF, and the actual TOF is a truly traveling time of theultrasound pulses; calculating a TOF shift wherein the TOF shift is adifference between the value of the calculated TOF and the value of thedetected TOF; and using the TOF shift to calculate the speed of themoving objects based on the equation of TOF shift.
 11. The method ofclaim 10 further comprising a method to correctly calculate the speed ofthe moving objects after the aliasing for the pulsed wave and the colorultrasound comprising: identifying an aliasing TOF, wherein as theactual TOF excesses its aliasing limit, the detected TOF ismisinterpreted by ultrasound system to generate the aliasing TOF, thealiasing TOF shift is on opposite site of the baseline and disruptscontinuity of a profile of the TOF shift, and a tip of a profile of thealiasing TOF shift is toward the baseline; obtaining a corrected TOFshift by rectifying the aliasing TOF shift to correct registration ofthe reflected ultrasound pulses after the actual TOF exceeds thealiasing limit, the tip of the profile of corrected TOF shift is awayfrom the baseline, and the corrected TOF shift reconstructs thecontinuation of the profile of the TOF shift; and using the correctedTOF shift to calculate the speed of the moving objects based on anequation of corrected TOF shift:${{Corrected}\mspace{14mu} {TOF}\mspace{14mu} {shift}} = \frac{2 \times V_{objects} \times f \times {\cos (\theta)}}{V_{avg}}$12. The method of claim 11, wherein for forward moving objects, thespeed of the moving objects is correctly calculated after the aliasingby: identifying the aliasing for the forward moving objects wherein thealiasing limit for the actual TOF is less than a value of halfcalculated TOF; after the actual TOF excesses the aliasing limit, theultrasound system misinterprets the detected TOF by adding a value ofone calculated TOF to a value of the actual TOF to form an aliasing TOF,the value of the aliasing TOF is greater than the value of the baselineand its TOF shift is located on an opposite site of the baseline, andthe aliasing TOF shift disrupts the continuation of the profile of theTOF shift, and the tip of the profile of the aliasing TOF shift istoward the baseline; obtaining the corrected TOF shift by subtracting avalue of the aliasing TOF shift from a value of the calculated TOF toreestablish the continuation of the profile of the TOF shift; and usingthe corrected TOF shift to calculate the speed of the forward movingobjects based on the equation of corrected TOF shift.
 13. The method ofclaim 11, wherein for reversely moving objects, the speed of the movingobjects is correctly calculated after the aliasing by: identifying thealiasing for the reversely moving objects wherein the aliasing limit forthe actual TOF is greater than the value of one and half calculated TOF;after the actual TOF excesses the aliasing limit, the ultrasound systemmisinterprets the detected TOF by subtracting a value of one calculatedTOF from a value of the actual TOF to form an aliasing TOF; the value ofthe aliasing TOF is smaller than the value of the baseline and thealiasing TOF shift is located on the opposite site of the baseline, andthe aliasing TOF shift disrupts the continuation of the profile of theTOF shift, and the tip of the profile of the aliasing TOF shift istoward the baseline; obtaining the corrected TOF shift by subtracting avalue of the calculated TOF shift from a value of the aliasing TOF shiftto reestablish the continuation of the profile of the TOF shift; andusing the corrected TOF shift to calculate the speed of the reverselymoving objects based on the equation of corrected TOF shift.
 14. Themethod of claim 10 further comprising a method of avoiding the aliasingby modifying the computer program in the ultrasound system to preventadding or subtracting a value of a calculated TOF from the detected TOFafter the actual TOF excesses its aliasing limit.
 15. The method ofclaim 11, further comprising a method of differentiating a color of thealiasing from a color of turbulent flows and rectifying the color of thealiasing for the color ultrasound comprising: identifying the aliasingTOF shift for the color of the aliasing wherein from the color of thealiasing to a edge of another color, the value of the TOF shift isgradually increased until close to the value of half calculated TOF, andthe profile of the aliasing TOF shift is more close to the value of halfcalculated TOF, and the tip of the profile of the aliasing TOF shift istoward the baseline; a color of no-aliasing represents a flow before itsactual TOF excesses the aliasing limit, the profile of the no-aliasingTOF shift is more closer to the baseline, and the tip of the no-aliasingTOF shift is away from the baseline; identifying the TOF shift for thecolor of turbulent flows wherein from one color to a edge of anothercolor, the value of the TOF shift is gradually decreased until close tozero, the tip of the profile of the TOF shift for the color of turbulentflows is away from the baseline; and rectifying the color of thealiasing wherein the aliasing TOF shift is corrected according to thedirection of the no-aliasing flow, and the color of the aliasing iscorrected based on the value of the corrected TOF shift.
 16. A method ofcalculation of the detecting depth and the moving speed of objects withcoding ultrasound pulses comprising: a transducer contains one pair ormore of emitting PZT elements and receiving PZT elements, assigningdifferent numbers of the ultrasound pulses within each pulse duration toform different pulse characters, a resting period is a time between eachadjacent pulse duration; the emitting PZT elements emit specificallycoded pulse characters, which endow information of a emitting time foreach pulse character, and the resting period for the emitted ultrasoundpulses keeps identical; the receiving PZT elements receive reflectedultrasound pulses, and decode received pulse characters to compare withthe emitted codes of the pulse characters, TOF is obtained from a timebetween the emitted pulse character and the same reflected pulsecharacter, and TOF shift is obtained from a time difference between theemitted resting period and the correspondingly received resting period;identifying motionless objects from the reflected ultrasound pulses withidentical value of the TOF and zero value of the TOF shift, therein thedepth of the motionless objects is calculated from the TOF; andidentifying moving objects from the reflected ultrasound pulses withvariable values of the TOF and the TOF shift, therein the speed of themoving objects is calculated with the equation of TOF shift, the depthof the moving objects is a half multiplication value of the sum of theTOF and the TOF shift with the average speed of ultrasound in thetransmitting medium, for forward moving objects, the TOF shift ispositive value, and for reversely moving objects, the TOF shift isnegative value, the equation of calculating the depth of the movingobjects comprising:depth of moving objects=V _(avg).×(TOF+TOF shift)/2
 17. The method ofclaim 16 further comprising improving noise and artifacts with codingultrasound pulses wherein by comparing the received codes of the pulsecharacters with the emitted codes of the pulse characters, thereflections that have the identical received codes of the pulsecharacters with the emitted codes of the pulse characters will beregistered to an area that belongs to the PZT element that emits thecodes of the pulse characters.
 18. A method of claim 1, furthercomprising applications in detecting a depth or a distance of objectswith sound pulses of any frequencies.
 19. A method of claim 6, furthercomprising applications in calculating a speed of moving objects withsound pulses of any frequencies.
 20. A method of claim 16, furthercomprising applications in detecting depth and distance and moving speedof objects with coded sound pulses with sound pulses of any frequencies.